Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$95.40	5.252%	$100.4104	$100.41	$100.40	$100.40
Purchase #2	$235.78	12.451%	$265.137	$265.14	$265.15	$265.10
Purchase #3	$136.95	8.618%	$148.7524	$148.75	$148.75	$148.80
Purchase #4	$66.84	10.120%	$73.6042	$73.60	$73.60	$73.60
Purchase #5	$32.61	13.666%	$37.0665	$37.07	$37.05	$37.10
Purchase #6	$222.78	5.307%	$234.6029	$234.60	$234.60	$234.60
Purchase #7	$222.91	3.622%	$230.9838	$230.98	$231.00	$231.00
7 purchase totals =	$1,013.27		$1,090.5572	$1,090.55	$1,090.55	$1,090.60